Railway signaling system



March 1941- R. R. KEMMERER RAILWAY SIGNALING SYSTEM 2 Sheets-:Sheet ,1

Filed July 31., 1940 RP. Y m% m mm w v T m m M 3 mm m l M l m Fig. 2.

Patented Mar. 18, 1941 RAIUWAY SIGNALING SYSTEM Ralph E. Kemmerer,Swissvale, Pa., assignor to The Union Switch & Signal Company Swissvale,Pa., a corporation of Pennsylvania 7 Application July 31, 1940, SerialNo. 348,937

16 Claims.

vide a signaling system of the type described.

and incorporating means to check the integrity of the lamps of themarkers and controlling the supply of energy to the sections in the rearso that if while a section is occupied the lamp of the marker for thatsection is defective, energy effective to produce a proceed indicationon the locomotive of a following train'will not be supplied to the railsof the adjacent section in the rear.

Another object of my invention is to provide an improved coded signalingsystem employing wayside signals, and having lightout protection meansarranged so that in the event a signal lamp is defective, the signalwill be conditioned to display its next most restrictive indication,while the energy supplied to the section in the rear will be changed soas to be commensurate with the indication displayed by the signal.

A further object of my invention is to provide a railroad signalingsystem having wayside signals controlled by coded track circuitapparatus, the signals being normally dark and being lighted on theapproach of a train, the equipment being arranged so that if the lamp ofa signal is defective, the coded energy supplied to the adjacent sectionin the rear will be altered so that a train in the section in the rearof the defective signal will receive a more restrictive indication thanit normally would.

Other objects of my invention and features of novelty will be apparentfrom the following description taken in connection with the accompanyingdrawings.

I shall describe three systems embodying my invention, and shall thenpoint out the novel features thereof in claims.

In the drawings Fig. 1 is a diagram showing a signaling system having amarker lamp at the entrance to each block and incorporating lightoutprotection means provided by my invention, and

Figs. 2 and 3 are diagrams showing wayside signaling systems employinglightout protection means provided by this invention.

Referring to Fig. 1 of the drawings, there is shown therein a stretch ofrailway'track having track rails I and 2 over which traflic moves 5 inthe direction indicated by the arrow, and which are divided by insulatedjoints 3 into the usual track sections. Two complete sections are shownand are here designated HT and UT.

The track stretch shown in Fig, 1 employs cab signals on the locomotivestraversing the track stretch, and does not have wayside signals exceptfor a marker M at the entrance to each block or track section.

The signaling system shown in-Fig. 1 is of the three-indication varietyand makes use of energy coded at two different code frequencies. Thiscoded energy is provided by code transmitters CT having two circuitmaking and breaking contacts and I80 which are operated at differentspeeds by a motor or other means so as to provide 75 or 180 energyimpulses per minute which are separated by periods of equal durationduring which no energy is supplied.

The system shown employs coded alternating current in the trackcircuits. This current may be suppliedirom any suitable source and maybe distributed throughout the track stretch by a transmission line, notshown, the. terminals of the source being designatedBX and CK.

- The cab signal apparatus adapted to be used in connection with thewayside'apparatus is not a part of this invention and any form ofequipment 'well known in the art may be employed. One form of apparatuswhich may be employed is shown in Letters Patent of the United StatesNo. 1,986,679 issued January 1, 1935, to Lloyd V.

Lewis.

Each of the track sections has a code following track relay TR at theentrance end of the sec- 40 tion and receiving energy over the sectionrails through a rectifier RX. Each of the track relays has associatedtherewith code detecting means comprising a transformer DT and a slowreleasing relay H, while, each marker lamp M has associated therewith alightout r'elay'LOR.

The equipment is shown in the condition which it assumes when sectionI2T and the sections in advance are vacant. At this time energy .of 18050 code frequency is supplied through-the track transformer IITT to therails of section HT by the means associated with the adjacent section inadvance. The equipment associated with the section in advance operatesin the same. manner as that associated with section HT, as hereinafterexplained in detail.

The energy supplied to the rails of section I [T feeds through therectifier IIRX to the track relay TR and produces code followingoperation of this relay so that the end portions of the primary windingof the transformer llDT are alternately energized from a local source ofdirect current, and current is induced in the transformer secondarywinding, while a contact of the track relay rectifies the energysupplied from the transformer secondary Winding to the relay III-I. Therelay H is of a type which is slow to release its contacts with theresult that its contacts remain picked up during the intervals betweenthe supply of impulses of energy thereto.

As relay H is picked up, its contact 2i! establishes the circuit tosupply energyvof 180 code frequency to the rails of the section in therear, while contact 2| interrupts the circuit of the marker lamp HM.

As energy of 180 code frequency is supplied to the rails of section I2T,the relay 12H is picked up and establishes the circuit to supply energyof 180 code frequency to the section farther in the rear, while thecircuit of the lamp [2M is interrupted.

As energy of 180 code frequency is supplied to the rails of the sectionin the rear of section IZT, the cab signal apparatus, showndiagrammatically, for a locomotive in that section will operate toprovide its green or clear indication.

If the locomotive advances into section I2T, the cab signal apparatus onthe locomotive will respond to the energy of 180 code frequency suppliedto the track rails toprovide the engineer with a clear signalindication.

On entrance of the locomotive into section lZT the track relay I2TR isshunted and ceases to respond to coded energy with the result thatenergy is no longer supplied through the transformer IZDT .to the relayIZH. On release of relay IZH contact 2| of the relayestablishesthecircuit of themarker lamp IZM, and if the filament of this lamp isintact so that the lamp is lighted, the lightout relay IZLOR will pickup as the winding of this relay is connected in series with the markerlamp. v

On picking up of the lightout relay IZLOR. the circuit for supplyingenergy of 75 code frequency to the section in the rear is established,and is traced from terminal BX of the source of alternating currentthrough contact 15 of the code transmitter T, front contact 23 of relayI2LOR, back contact 20 of relay l2I-I and primary winding of the tracktransformer I3TT to terminal OX.

When the train advances into section I IT, the equipment associated withthis section operates in the manner explained in connection with sectionI 2T so that energy of '75 code frequency is supplied to the rails ofsection I2T, while the marker lamp HM is lighted.

As long as any portion of the train remains in section IZT, the trackrelay IZTR is shunted'so that energy of '75 code frequency is suppliedto the section in the rear, while the marker lamp I2M is lighted toindicate to a following train that section IZT is occupied.

In addition, as long as any portion'of the train remains in section I2T,the track rails are shunted and coded signal control current does notflow in the rearward portions of the track rails ofsection I2T so thatif a following train should code frequency thereto.

enter this section, the cab signal apparatus on the locomotive of thetrain would be conditioned to display its most restrictive or stopindication.

When the rear of the train vacates section IZT, the energy of 75 codefrequency feeds to the track relay IZTR and produces code followingoperation of this relay with the result that energy is supplied throughthe transformer |2DT to the relay HE, and contact 20 is picked up tointerrupt the circuit for supplying energy of '75 code frequency to thesection in the rear and to establish the circuit for supplying energy ofIn addition, contact 2| of relay I2I I is picked up so that the markerlamp I 2M is extinguished, while the lightout "relay I ELOR releases.

maintain the supply of energy of 180 code fre- H .quency. to the sectionin the rear.

Operation'of equipment show'rt in Fig. 1 if a marker lamp is defectiveThe equipment provided by this invention includesmeans tocheck theintegrity of the filaments ofthe marker lamps so that if one of theselamps fails ,to light when it should, the energy supplied to the sectionin the rear will be controlled so that the cab signal apparatus on atrain entering th section in the rear will not receive. a proceedindication, but instead will receive the stop or. most restrictiveindication.

For purposes of illustration it will be assumed that a train enterssection .I IT and that the lamp of the marker lamp MM is. defective andfails to light.

Whenthe. train enters section HT, the track relay l I TR is shunted andenergyisno longer supplied through transformer MDT to the relay l |.H,and' this relay releases so that contact 20 interrupts the. circuit forsupplying energy of 180 code frequency to the rails of section IZT.

In addition, contact 2! of relay H is released and establishes thecircuit of the lamp 1 l M, but as it is assumed that the lamp isdefective, this lamp is not lighted While the relay l ILOR is notenergized and its contact 23 remains released. Accordingly, energy of'75 code frequency is not supplied to the rails of section I2T, andinstead steady energy is supplied thereto over a circuit which is tracedfrom terminal BX, over back contact 23 of-relay lILOR,'back contact 20of relay IIH, and the primarywinding of transformer I2TT.

When the train under consideration vacates section IZT, thissteadyenergy will feed to the track relay I2TR and keep it steadilyenergized so that energy is not supplied through the transformer I2DT tothe relay IZH and this relay is released to light the lamp IZM and toeffect the supply of energy of '75 code frequency to the section in therear.

Accordingly, a second or following train will receive a restrictiveindication when it enters the section in the rear of section IZT, Whileit will be warned by the marker lamp I2M when it reaches sectionlZT. Ifthe train advances into section IZT, the cab signal equipment on thelocomotive 'will give the most restrictive indienergy wil1 no longerbesupplied through the decoding transformer MDT to the relays NIH and NJ.

On release of relay MI-I contact 30 interrupts the circuit of the lamp Gand establishes the circuit of the lamp R of signal MS. .The circuit ofthe lamp R is traced from terminal B through back contact 39 'of relay Ill-I, winding of lightout relay iRLO, and lamp R to terminal C. If thelamp R is not defective and becomes lighted, the relay IQRLO will beenergized and its contact 35 is picked up and interrupts the circuit ofthe marker lamp M.

In addition, on release of the relay 14H contact 3 3 interrupts thecircuit for supplying energy of 180 code frequency to the rails ofsection IGT, and establishes the circuit for supplying energy of '75code frequency to section -|5T. This circuit is traced from terminal BXthrough code transmitter contact 75, and back contact 3 1 of relay Mil-Ito the primary winding of transformer l5TT.

As long as the train is in section MT, the cab signal equipment on thelocomotive, if the locomotlve is provided with this equipment, willcontinue to receive energy of 180 code frequency supplied by theequipment associated with section LiT and the cab signal equipment willdisplay its clear indication.

When the train advances into section I3T, the equipment associated withthat section Will operate as described in detail in connection withsection l iT to supply energy of code frequency to the rails of sectionMT, and tocondition the signal its to display its red or stopindication.

When the train clears section I 4T, energy of 75 code frequency feeds tothe track relay MTR, and this relay operates to supply energy throughthe transformer l-DT to the relay HI-I. As the track relay is respondingto energy of the '75 code frequency, too little energy is suppliedthrough the resonant unit HiRU to pick up the relay MJ.

On picking up of relay MEI contact 30 interrupts the circuit tracedabove for lighting the red lamp R and establishes the circuit of theyellow or caution lamp Y of signal MS. This circuit is traced fromterminal B over front contact 38 of relay ii-I, back contact 3! of relay5 ZJ, winding of lightout relay I l-2L0, and lamp Y to terminal C. Ifthe lamp Y lights as it should, the relay l lYLO will be picked up sothat the circuit for supplying energy" of code frequency to the sectionin the rear is established. This circuit is traced from terminal BX overcontact 8% of the code transmitter, front contact 36 of relay i iYLO,back contact 33 of relay lGLo, and front contact 3 of relay MH to thetransformer I5TT.

When the train vacates section HST, the track relay for this sectionresponds to energy of 75 code frequency, while the energy supplied tosection MT is changed to 180 code frequency. On this change in thefrequency of the energy supplied to section lfiT the track relay I5TRoperates at a higher speed and sufficient energy is supplied through theresonant unit MRU to pick up the relay MJ.

When relay MJ picks up, its contact 3! interrupts the circuit of theyellow lamp Y and of the relay MYLO, and establishes the circuit of thegreen lamp G and of the relay I ZGLO. On picking up of the relay MGLOits contact 33 interrupts the circuit traced above for supplying energyof 18.0 "codefrequencyto section HT, and

-establishes'a connectionshunting the contact.36

of the relay MYLO so that energy of 180 code frequency continues to besupplied to section I 5T.

Operat on of system shown in Fig. 2 in the event a signal lamp isdefective The system provided by' this invention is arranged so that ifany one of the signal lamps is defective and fails to light when itshould, the lamp for the next most restrictive indication will belighted, while the energy supplied to the section in the rear iscontrolled so as to be consistent with the aspect displayedby thesignal.

If, for example, the green lamp G of signal MS is defective and does notbecome lighted when the relays MH and NJ are picked up, the relay MGLOwill be released and its contact 38 will establish a circuit to "lightthe yellow lamp Y. This .circuit includes front contact 30 of relay il-H, back contact 38 of relay MGLO, winding of relay MYLO, and lamp Y.At this time the relay I lGLO is released and the relay MYLO is pickedup so that a circuit is established to supply energy of 180 codefrequency to section I5T. This is'the code frequency which it is properto supply to section I5T when the signal MS is displaying-its yellow orcaution indication.

The system is also arranged so that if the yellow light Y is defectiveand does not become lighted when it should be, the red lamp R will belighted, While the energy supplied to the section in the rear will bechanged from 180 to '75 code frequency.

The yellow lamp should be lighted when the relay I 4H is picked up andthe relay NJ is released, or when the relay Iii-I is picked up and therelay MGLO isreleased. In either case the relay MYLO will be picked upif the lamp lights, but'will be released if the lamp fails to light.

When the relay MYLO is released at a time when the relay MGLO isreleased, a circuit is established to light the red or stop lamp R. Thiscircuit is traced from terminal B through back contact 39 of relay MYLO,back contact 40 of relay I4GLO, winding of relay l iRLO, and lamp R toterminal C. I

In addition, when relay l' l-YLO releases at a time when relay MGLO isreleased and relay 14H is picked up, a circuit is established to supplyenergy of 75 code frequency to the section in the rear. Thiscircuit istraced from terminal BX over code transmitter contact l5, back contact36 of relay MYLO, back contact 33 of relay MGLO, and front contact 34 ofrelay MH to the track transformer I5TT.

If the red lamp R is intact and becomes lighted, the relay MRLO will bepicked up and contact 35 will interrupt the circuit of the marker lampM.

It will be seen, therefore, if for any reason the yellow light Y failsto light when it should, the red light R will be lighted instead, whilethe energy supplied to the section in the rear will be changed from"180to 75 code frequency. This will cause the signal for the section in therear to change its indication from green to yellow so that a followingtrain will receive a caution indication at the entrance to section MTand will not approach the signal MS at full speed at a time when thesignal MS is displayingits red or stop cation in response to thepresence of steady uncoded energyin the rails of section I2T.

As the following train receives the most restrictive indication when itreaches section lZT, it will be moving at very slow speed when itapproaches themarker lamp HM, and failure ofthis lamp to be illuminatedwill not create a serious hazard as the train will be able to stopbefore striking the train present in section HT.

When the first train vacates section IIT, the track relay IITR respondsto coded energy and relay Ill-I picks up to interrupt the supply ofsteady energy to the rails of section IZT, and to establish the circuitto supply energy of 180 code frequency to the rails of section |2T inthe usual manner.

From the foregoing it will be seen that when the marker lamp of anoccupied block is defective, the energy supplied to the section in therear is controlled so that a following train will receive the mostrestrictive signal indication one block before it reaches the defectivelamp. This insures that the following train willreduce its speed so asto be able to stop before entering the occupied block.

If the energy supplied to the rails of the section at the rear of asection having a defective marker lamp were not controlled in thismanner, a following train would receive a proceed indication in thesection in the rear of the defective lamp and would be traveling at asubstantial speed when it approached the defective lamp, and theengineer might not see the lamp since the lamp would not be lighted asit should be. Accordingly, the engineer of the second train would notknow when he reached the entrance of the occupied block and wouldcontinue on into the occupied block. After the locomotive of the secondtrain enters the occupied block, the cab signal equipment carried by itwill give the most restrictive indication.

However, if the first train stopped with the rear end thereof adjacentthe entrance end of section HT, the second or following train might notbe able to stop soon enough after entering the occupied section andreceiving the stop indication to avoid hitting the first train.

As the system provided by this invention provides a marker lamp to markthe entrance to an occupied block, following trains are warned when theyapproach an occupied section and can stop before entering the section orbefore reaching a train in the section.

Furthermore, the system is arranged so that if the marker lamp is notilluminated when it should be, the supply of coded energy to the sectionin the rear is cut off, while the marker lamp at the entrance of thesection in the rear is lighted and the energy supply to the rails ofthat section is controlled to cause the cab signal equipment on alocomotive in the section in the rear of the defective lamp to. displayits most restrictive indication.

It will be seen, therefore, that the system provided by this inventionprovides a maximum degree of safety both when the system is functioningas intended, and when thelamp of one of the marker lamps is defective.

The means provided by this invention for controlling the supply of codedenergy to the section in the rear is applicable to a signaling systememploying wayside signals, and Fig. 2 is a diagram showing thisapplication of the invention.

'Construction and operation of modification shown in Fig. 2

Referring to Fig. 2, there is shown therein a stretch of railway trackemploying wayside signals of the color light type. One block section,identified as section MT, together with portions of two other sections,is shown.

Each of the track sections has at the entrance end thereof a waysidesignal having a green or clear lamp G, a yellow or caution lamp Y, a redor stop lamp R, and a marker lamp M which may be of any distinctivecolor.

The system shown in Fig. 2 makes use of coded energy of two codefrequencies in the track circuits thereof, while it has decoding meanssimilar to the code detecting means employed in the system shown in Fig.l.

The equipment is shown in Fig. 2 in the condition which it assumes whenthe track stretch is vacant. At this time energy of 180 code frequencyis supplied to the rails of section I4T by the equipment associated withthe adjacent section in advance, while this energy feeds through therectifier MRX to the track relay MTR and produces code followingoperation of this relay.

As a result of code following operation of the track relay MTR, the twoend portions of the primary winding of the decoding transformer MDT arealternately energized from a local source of direct current, not shown,and energy is induced in the secondary windings of the transformer,while a contact of the track relay rectifies the energy supplied fromone of these secondary windings to the winding of relay 14H. Energy issupplied from the other secondary winding of the transformer MDT througha resonant rectifier unit MRU to the relay NJ.

The resonant unit RU includes a capacitor and an inductance which arearranged and proportioned so as to pass energy suificient to operate therelay J when the track relay is responding to energy of 180 codefrequency and to pass too little energy to operate the relay J when thetrack relay is responding to energy of a different code frequency, suchas '75 code frequency. The unit RU includes a rectifier which convertsinto direct current the alternating current supplied through the unit.

As the track relay MTR. is responding to energy of 180 code frequency,the relays MH and J are both picked up, and the green or clear lamp G ofsignal MS is lighted by current supplied over the circuit which istraced from terminal B of a local source of direct current through frontcontact 30 of relay MH, front contact 3| of relay NJ, winding oflightout relay MGLO, and lamp G to terminal C.

As the relay NIH is picked up, the circuit for supplying energy of 180code frequency to the section in the rear is established, and is tracedfrom terminal BX of the source of alternating current signal controlenergy through contact I of code transmitter MCT, front contact 33 I ofrelay MGLO, front contact 34 of relay NH, and primary winding of tracktransformer IS'II to terminal CX.

As energy of code frequency is supplied to the rails of section l5T, thesignal, not shown, for that section is conditioned to display its greenor clear indication, while the cab signal equipment of a locomotivepresent in section l5T will display its clear indication.

If a train moving in the normal direction of traffic, that is from leftto right, enters section MT, it will shunt the track relay TR. and

lighted, while steady uncoded energy will be supplied to the section inthe rear.

The red lamp R of signal S should be lighted when the relay l lH isreleased, or when relay MH lamp M, while contact 42 will establish acircuit.

to supply steady energy to the section in the rear.

One circuit of the marker lamp M is traced from terminal B through backcontact 39 of relay MYLO, back contact 40 of relay MGLO, and backcontact 35 of relay MRLO to lamp M. Another circuit for the marker lampis traced from terminal B through back contact 39 of relay MYLO, backcontact 40 of relay MGLO, and back contact 35 of relay MRLO and lamp Mto terminal 0.

The circuit for supplying steady energy to section I5TT is traced fromterminal BX through back contact 42 of relay MRLO and thence over backcontact 34 of relay MH, if this relay is re.- leased. If relay MI-I ispicked up, the circuit for supplying steady energy to the section in thefear is traced from terminal BX over back'contact 42 of relay MRLO, backcontact 36 of'relay MYLO, back contact 33 of relay MGLO, and frontcontact 34 of relay H. In either case the circuit for supplying energyof '75 code frequency is maintained, but the steady energy supplied overback contact 42 of relay MRLO fills in the off periods in the code sothat the code is ineffective.

On the supply of steady energy to the rails of section I5T the trackrelay for that section is steadily picked up with the result that theredor stop lamp of the associated signal is lighted, while energy of 75code frequency will be supplied to the section farther in the rear tocondition the signal for that section to display its caution indication.

Accordingly, a-following train will receive a caution indication twoblocks before it reaches the signal with the defective lamp, and willreceive a stop indication one block before it reaches that signal. Thetrain, therefore, will be traveling at slow speed when it reaches thesignal at which the marker lamp is lighted and the engineer will haveample time to stop before striking a train in advance of the markerlamp. The marker lamp serves to identify the signal and shows thelocation of the signal, and also marks the entrance to an occupiedblock.

From the foregoing it will be 'seen that the system provided by thismodification of the invention is arranged to check the integrity of thelamps of the wayside signals, and that in the event one of these isdefective, the lamp providing the next most restrictive indication islighted, while the energy supplied to the section in the rear is changedto that proper for that signal indication.

Construction and operation of modification shown in Fig. 3

In the system shown in Fig. 3, the lamps of the signals are normallydark, and are lighted on entrance of a train into the section in therear of the signal. Any desired means for approach lighting may beemployed to control the circuits of the signal lamps. The means shown inthe drawings is substantially the same as that shown in Letters Patentof the United States No. 2,174,255 to Herman G. Blosser.

Referring to Fig. 3 of the drawings, there is shown therein a stretch ofrailroad track having track rails l and 2 which are divided by insulatedjoints 3 into the customary successive track or block sections. Onecomplete section, which is identified as section I8T, together withportions of the adjoining sections is shown.

Each of the track sections has at the entrance end thereof a waysidesignal S together with a track relay and decoding means for controllingthe signal, and, in addition, means for controlling the supply of codedenergy to the section in the rear.

The equipment is shown in the condition which it assumes when the trackstretch is vacant. At this time energy of 180 code frequency is suppliedto the coding relay I'ICTM in the manner hereinafter explained inconnection with section I8T, and the contacts of this relay are pickedup and released at this rate.

As a result of code following operation of the coding relay IICTMimpulses of master code energy are supplied from the track battery I8TBto the rails of section I8T during the picked-up periods of the relaycontacts, while during the released periods of'the relay contactsconnection is established to permit impulses of feed back energy to besupplied from the section rails to the pick-up winding 41 of the relayIIAR, and to also establish a circuit to supply energy from the batteryI8TB to the holding winding 52 of the relay AR and to the winding of therelay ll'AP when cont-act 5| of relay l'lAR picks up.

The master code energy supplied to the rails of section I8T feeds to thetrack relay IBTR and causes code following operation of this relay withthe result that energy is supplied through the decoding transformer |8DTto therelay I8H and also to the impulse relay I8IR. As a result of thesupplyv of energy to the impulse relay 181R this relay operates todisconnect the track relay l8TR. from the rails of section I8T and tosupply impulses'o-f feed back energy from the battery IBAB to the railsof section I8T during the ofi periods in the master code supplied to therails of section IST.

As long as the track section is vacant, therefore, the track relay IBTRresponds to master code energy, While feed back energy is supplied overthe section rails to the relay I'IAR which energizes the slow releasingrelay IIAP.

The construction and operation of this portion of the system is not apart of this invention and is described in detail in the patent toBlosser, identified above.

The relay HAP has associated therewith a slow releasing repeater relayIIAPP which is energized when the relay I'IAP is picked up. The relays I(AP and I'IAPP together control the lamp of the signal HS, and alsocontrol the supply of energy to the decoding unit associated with thetrack relay for section "T for detecting when the relay is responding toenergy of 180 code frequency. The operation of this portion of theapparatus is best understood by reference to the corresponding apparatusassociated with section l8T.

As the track stretch is assumed to be vacant,

the relays [BAP and IBAPP are energized inthe manner explained in detailabove, and the circuit for supplying energy to the primary winding ofthe decoding transformer IEDTA is interrupted by contact 56 of relayIBAP. Accordingly, energy is not supplied from this transformer to relayIBJ and the relay NJ is released. As the circuit of the decodingtransformer I8DTA' is interrupted when section I9T is vacant, no energyis consumed by this transformer and the resonant rectifier unit IERUA;and there is a substantial saving of current for this reason. As long assection I9T is vacant, the signal ISS is dark and there is no need toenergize the relay IBJ.

At this time the circuit of the lightout relay IBLOR and of the lamp IBLof signal IBS is interrupted by contact 56 of'relay IBAPP and by contact59 of relay IBAP, while the circuit of the 180 code transmitter ISCTA isestablished as'contact SI of relay |8APP and contact 62 of relay I8H arepicked up. The contact 180 of code transmitter I8CTA, therefore, isoperated to establish and interrupt the circuit of the coding relayIBCTM 180 times a minute. The circuit of the coding relay IBCTM iscomplete at this time as contact 65 of relay NH and contact 66 of relayI8AP are picked up. The coding relay ISCTM, therefore, operates tosupply master code energy of 180 code frequency to the rails of sectionlfi'I.

At this time as the contact 68 of relay WA? is picked up, the circuitfor supplying energy to the operating mechanism ISG of the signal IBS isinterrupted.

From the foregoing it will be seen that when section IST is vacant, therelays I8AP and |8APP are energized with the result that the signal I88is dark, the operating mechanism of the signal is deenergized, and thedecoding transformer I8DTA is deenergized.

When a train traveling in the normal direction of trafiic, that is fromleft to right, enters section I9T, it shunts the track relay, not shown,for that section with the result that feed back energy is no longersupplied to the rails of the section and the relay IBAP releases.Release of contact 54 of this relay establishes the circuit forsupplying alternating current energyto the track transformer ISTT sothat coded cab signal energy is thereafter supplied from any suitablesource of alternating current, the terminals of which are designated BXand CK, to the rails of section NET to operate the cab signal equipmenton the locomotive of the train which has entered this section. Thealternating current energy supplied to the rails of section lliT iscoded at the rate determined by the coding relay ISCTM,

and this relay is operating at this time to provide the 180 codefrequency so that the cab signal equipment will be conditioned todisplay its clear indication.

In addition, on release of relay ISAP, contact 58 interrupts the circuitof relay IBAPP and establishes the circuit for supplying energy to thesignal mechanism I8G. The relay IBAPP is slow releasing and its contactsremain picked up for a substantial time interval after release of relayIBAP. Accordingly, on release of the relay |8AP the circuit forsupplying energy to the primary winding of the transformer IBDTA isestablished. This circuit is traced from terminal B of a local source ofdirect current, not shown, through front contact 58 of relay IBAPP, backcontact 56 of relay I8AP, and front contact HI.v of relay IBH to contactH of the track relay i8TR. which alternately establishes connection withthe two end terminals of the transformer primary winding, while thecenter terminal of this winding is connected to terminal C of the sourceof current.

As soon as the circuit for supplying energy to the transformer ISDTA iscompleted, energy is induced in the transformer secondary winding and issupplied therefrom through the resonant rectifier unit I8RUA to pick upthe relay I8J. Picking up of the contacts 13 and M of relay lilJ changesthe polarity of the energy supplied to the signal mechanism [8G to causeit to condition the signal to display its green or clear indication. Thecircuit for energizing the mechanism I8G is traced from terminal Bthrough back contact 63 of relay I8AP, front contact 16 of relay IBI-I,front contact 13 of relay I8J, signal mechanism IBG, and front contact14 of relay IBJ to terminal 0.

On expiration of a short time interval after release of relay I8AP therelay ISAPP releases. This time interval is long enough to permit therelay I8J to pick up and to permit the mechanism of signal I8G toposition itself before relay I8APP releases.

On release of relay IBAPP, contact 53 interrupts the circuit tracedabove for energizing the transformer I8DTA, and establishes the circuitof the lig'htout relay IBLOR and the lamp ISL. This circuit includesback contact 58 of relay IBAPP and back contact 59 of relay ISAP.

If the lamp I SL is in good condition and becomes lighted, the lightoutrelay I8LOR will be energized and its contact 'l'l will pick up andestablish a circuit to supply energy to the transformer IBDTA so thatenergy continues to be supplied to the relay I8J. There is a shortinterruption in the supply of energy to the transformer IBDTA from thetime at which relay IBAPP releases and the time at which relay I8LORpicks up. The relay "U is slow releasing, however, and remains picked upduring this time interval.

In addition, on release of relay ISAPP, contact 6| interrupts thecircuit traced above for energizing the code transmitter IBCTA, but onpicking up of the relay I8LOR its contact 19 establishes a circuit toenergize the code transmitter I8CTA so that the code transmittercontinues to operate.

Release of contact 66 of relay I8AP interrupts the circuit traced abovefor energizing the coding relay I8CTM, but another circuit forenergizing this relay with energy of 180 code frequency is establishedon picking up of the relay I8LOR so that energy of 180 code frequencycontinues to be supplied to the coding relay l8CTM and this relaycontinues to supply energy of 180 code frequency to the rails of thesection in the rear. The circuit for supplying energy to the relay IBCTMis traced from terminal B through contact I of code transmitter I8CTA,front contact 8i of relay IBLOR, front contact 88 of relay 18H and backcontact 65 of relay I8AP to the relay I8CTM.

From the foregoing it will be seen that when a train enters section IQT,the relays ISA]? and I'8APP become released and establish the circuit ofthe transformer I8DTA so that the relay IBJ is energized, while energyis supplied to the signal mechanism I 8G to condition the signal todisplay its clear indication. In addition, alternating current energyissupplied to the rails of section I'ST to operate the cab signalapparatus on the locomotive to provide a clear cab signal, while energyis supplied to the lamp IBL of the signal IBS to light the lamp andcause the signal to display its clear indication.

When the train advances into section l8T, the track relay |8TR isshunted and energy is no longer supplied through the transformers I8DTand IBDTA to the relays I8H and |8J and these relays release. Release ofcontact 16 of relay I8H interrupts the circuit for energizing the signalmechanism I8G, and this mechanism thereupon conditions the signal N36 todisplay its red or stop indication.

On shunting of the track relay I8TR. energy is no longer supplied to theimpulse relay IBIR and this relay no longer supplies impulses of feedback energy to the rails of section I8T. Accordingly, the relays MAP and"AP? become released andcondition the signal ITS to display its clearindication, while alternating current cab signal control energy issupplied to the rails of section I8T.

In addition, on shunting of the track relay IBTR and release of therelay NH a circuit is established to energize the code transmitter ISC'I'B which provides impulses of energy of '75 code frequency. Thecircuit of this code transmitter is traced from terminal B through backcontact 6| of relay I8APP, back contact of relay 18H, and front contactof relay I8LOR tothe code transmitter NOTE. The contact 15 of thetransmitter I 8CTB is operated, therefore, to supply energy of '75 codefrequency to the coding relay I8CTM over the circuit which is tracedfrom terminal B through contact 15, front contact 81 of relay IBLOR,back contact 88 of relay [8H, and back contact 66 of relay IBAP. Thecoding relay I8CTM, therefore, operates to supply impulses of mastercode energy of the '75 code frequency to the rails of section I9T, andwhen the train vacates section IST, these impulses of master code energyfeed to the track relay for section I 9T, while the impulse relayassociated therewith then operates to supply impulses of feed backenergy to the section rails as previously explained in connection withsection MT.

,The impulses of feed back energysupplied to section l9T cause the relayI8AP to pick up and its contact 68 establishes the circuit to supplyenergy to the relay I8APP to pick it up, while contact 68 interrupts thecircuit of the signal mechanism I8G.

On picking up of relay I8AP, contact 54 interrupts the supply ofalternating current cab signal control energy to the rails of sectionIBT, wlhile contact 66 interrupts the previously traced circuit forsupplying energy of 75 code frequency to the coding relay i8CTM andestablishes another circuit for supplying energy thereto. This circuitis traced from contact 15 through back contact 65 of relay I8H and frontcontact 66 of relay I8AP.

On picking up of relay ISAP, contact 59 inter rupts the circuit of thelamp I8L and of the relay l8LOR so that the lamp is extinguished and therelay ISLOR releases and its contact 85 interrupts the circuit forsupplying energy to the code transmitter IBCTB. However, on picking upof relay I8APP, its contact 6| establishes a circuit which includes backcontact 62 of relay l8H for energizing the code transmitter I8CTB and itcontinues to operate so that energy of 75 code frequency is supplied tothe rails of section |.9T to condition the signal for enter section I9Tand release the relays ISAP and I8APP so that lam-p I8L is lighted, thesignal IBS will display its red or stop indication.

When the train under consideration, that is the train in section IBT,advances into section HT, the track relay for that section is shuntedand the equipment associated therewith operates in the manner explainedin connection with section I8T to supply mastercode energy of '75 codefrequency to the rails of section MT and to condition the signal [TS todisplay its stop indication whenthe signal lamp is lighted.

When the train vacates section IBT, coded energy is supplied to thetrack relay I8TR and energy is suppliedthrough the transformer I8DT tothe relay I8H and also to the relay I8IR so that relay I8H picks up,while the relay IBIR supplies impulses of feed back energy to thesection rails to produce code following operation of the relay I'iAR.with resultant energization of the relays HA]? and llAPP.

When the relays HAP and llAPP are picked up, the circuit of the lamp ofthe signal ITS is interrupted, while the supply of alternating currentcab signal control energy to section |8T is cut off.

When relay I8H picks up, its contact 62 interrupts the circuit forenergizing the transmitter I 8CTB and establishes the circuit forenergizing the transmitter IBCTA, assuming that the contact 6| of relay|8APP is picked up, and this transmitter operates to supply energy ofcode frequency.

In addition, on picking up of the relay I8H its contact 65 interruptsthe circuit through which energy of '75 code frequency has been suppliedto the coding relay IBCTM and establishes a circuit to supply energy of180. code frequency thereto. The relay I8CTM, therefore, operates at thehigher rate and supplies master code impulses of 180 code frequency tothe rails of section IST.

If at this time a second or following train should enter section [QT andrelease the relays I8AP and IBAPP and establish the circuit of thetransformer I8DTA, too little energy would be supplied through theresonant rectifier unit I8RUA to pick up the relay l8J since the trackrelay IBTR is responding to energy of 75 code frequency. The relay I8J,therefore, would remain released and the polarity of the energy suppliedto the signal mechanism. I8G would be such as to condition the signal todisplay its yellow or caution indication when the signal lamp islighted. The circuit for supplying energy to the mechanism I8G would becomplete at this time as contact 68 of relay I8AP is released andcontact 16 of relay 18H is picked up.

It will be seen, therefore, that if a second or following train enterssection I 91 at a time when section I8T is vacant and section HT isoccupied, the signal I 8S will be conditioned to display its yellow orcaution indication, while mastercode energy of 180 code frequency willcontinue to be supplied to the rails of section |9T.

When the train under consideration advances far enough to vacate sectionHT, the track relay for this section responds to energy of '75 codefrequency with the result that the energy supplied to section EST ischanged from 75 to 189 code frequency. On this change in the energysupplied to the relay IZZTR this relay operates at a more rapid rate andif a train enters section IT the frequency of the ener y supplied fromthe transformer lfiDTA will be such that sufficient energy will besupplied through the resonant unit IBRUA to pick up the relay I SJ tothereby condition the signal IBS to display its clear indication.

On this change in the code supplied to the relay ESTR energy of 180 codefrequency continucs to be supplied to the rails of section iST.

Operation of the equipment shown in Fig. 3 in the event a signal lamp isdefective The system provided by this modification of the invention isarranged so that if the signal lamp of a signal is defective and doesnot become lighted when it should, the energy supplied to the section inthe rear will be controlled so that the signals in the rear of the onewith the defective lamp will display more restrictive indications thanthey normally would.

When the track stretch is vacant, energy of 180 code frequency issupplied to the track relay I8TR, and when a train enters section I9T,the relay iSAP releases and interrupts the circuit of the relay I SAPP.

On release of relay ISAPP, the circuit of the transformer itDTA isinterrupted, while a circuit is established to supply energy to the lampI8L and the relay HZLOR. If the lamp is defective, no energy will flowin this circuit and the relay IELOR will remain released, while itscontact T? will not establish the circuit to supply energy to thetransformer I8DTA. Accordingly, energy will not be supplied to the relayNJ and the polarity of the energy supplied to the signal mechanism ISGwill be such as to condition the signal to display its yellow or cautionindication instead of its clear indication.

The equipment is also arranged so that at this time operation of thecode transmitter I8CTA is discontinued, while opei ation of the codetransmitter lSCTB is initiated. On release of contact SI of relay ISAPPthe circuit of the code transmitter IQCTA is interrupted, while acircuit including back contact 6| of relay I8APP, front contact 80 ofrelay ISI-I, and back contact 19 of relay iSLOR, is established toenergize the code transmitter GBCTB to cause it to operate and provide'75 code for the coding relay lBCTM.

From the foregoing it will be seen that on entrance of a train intosection IST at a time when the track stretch is otherwise Vacant andwhen the lamp of the signal IBS is defective, the energy supplied to thecoding relay |8CTM is changed from 180 code frequency to 75 codefrequency with the result that energy of '75 code frequency is suppliedto the rails of section IST. Accordingly, the cab signal equipment onthe locomotive of the train in se tion IQT will be conditioned todisplay its caution indication instead of its clear indication and theengineer will reduce the speed of the train soas to be prepared to stopwhen he reaches signal l 853.

In addition, at this time the signal [BS is conditioned to display itsyellow or caution indicae tion, if the signal lamp were lighted, so thatany light reflected through the optical system of the signal will beyellow which will be consistent with the indication displayed by thelocomotive cab signal apparatus.

When the train. enters section ldT, the track relay IETR isshunted andrelay I8l-l becomes released and its contact 76 interrupts the circuitof the signal mechanism EEG and the mechanism conditions the signal 588todisplay its stop indication provided the signal lamp were lighted.

On release of relay I8H contact 88 interrupts the circuit traced abovefor supplying energy of 75 code frequency to the coding relay IBCTM,while contact 80 of relay ISH interrupts the circuit for supplyingenergy to the code transmitter IBCTB. As a result, therefore, energy isnot supplied to the coding relay KBC'I'M and this relay does not operateto supply coded energy to the rails of section MT. The track relay forsection lST, therefore, will remain released after the train vacatessection EQT, while no impulses of feed back energy will be supplied tothe section rails and the relays ISA? and ISAPP will remain rel-eased.

When the train under consideration entered section lH'I', the trackrelay for that section was shunted and the equipment associatedtherewith operated as heretofore described in connection with sectionI8T to supply energy of '75 code frequency to the section in the rear.Accordingly, when the train vacates section I 9T the track relay ISTRcontinues to be released as master code energy is not supplied to thesection rails, and energy of 75 code frequency continues to be suppliedto the rails of the adjacent section in the rear of section IST.

If, therefore, a second or following train should enter the section inthe rear of section I9T at a time when section NT is vacant and sectionIBT is occupied and the lamp of signal I88 is defective, the train willreceive a caution indication from the wayside signal at the entrance tothe section in the rear of section I9T, while the locomotive cab signalapparatus will also operate to provide its caution indication.

When the second or following train advances into section IQT at a timewhen section I9T is vacant and section IBT is occupied, the cab signalequipment on the locomotive of the train will operate to give its stopor most restrictive indication since at this time the coding relay IBCTMis not operating to supply coded energy to the rails of section IBT.

At this time as section HST is assumed to be occupied, the relay IBH isreleased and its contact l6 interrupts the circuit of the signalmechanism IBG with the result that the signal I8S is conditioned todisplay its red or stop indication, if the signal lamp were lighted, andany light reflected through the optical system of the signal will bered, which is consistent with the signal displayed by the cab signalequipment of a locomotive in section IQT.

In like manner, if a second or following train should enter sectionle'l'. after the first train has vacated section [8T and occupiessection HT, the second train will receive a caution cab signal, whilethe signal His will be conditioned so that yellow light will bereflected therefrom.

When the first train occupies section l'iT, the equipment associatedwith that section operates as heretofore explained to supply master codeenergy of vF75 code frequency to the rails of section IST, and the trackrelay TR. responds to this energy so that energy is supplied through thetransformer ISDT to the relay 18H.

On picking up of relay -l-8H contact 80 establishes a circuit to supplyenergy to the code transmitter IBCTB, while'contact 88 of relay [8Hestablishes a circuit to supply energy from the code transmitter I8CTBto the coding relay I8CTM. The circuit for energizing the transmitterlBC'I'B is traced from terminal .13 over back contact Bl of relay|-8APP, front contact 810 of relay 181-1, and back contact 19 'ofrelayI.8LOR, while the circuit for supplying energy to the coding relay I8CTMis traced from terminal B over contact 15 of the code transmitterIBC'IB, back contact .81 of relay I8LOR, front contact of relay h'iI-I,and back contact 66 of relay IBAP.

As a result of the supply of energy to the coding relay I BCTM thisrelay supplies master code energy of 75 code frequency to the rails ofsection IBT, and if at this time the section is vacant, the track .relaywill respond to this coded energy, while feed back energy willbesupplied over the section rails so that the relays |8AP and ISAPP becomepicked up.

On picking up of relay IBAPP contact 61 interrupts the circuit tracedabove for energizing the code transmitter ItCTB and establishes acircuit including front contact 62 of relay IBH for energizing the codetransmitter JBCTA. In addition, on picking up of relay IBAP contact 66interrupts the circuit traced above forsupplying energy of 75 codefrequency to the coding relay lSCTM and establishes a circuit includingfront contact 65 of relay [8H for supplyin energy of 180 code frequencyto the coding relay IBCTM so that the energy supplied to section |9T ischanged from '75 to 180 code and the signal for section IBT will displayits clear indication when the section in the rear thereof becomesoccupied. This is proper as the sections IBT and IQT are assumed to bevacant.

If at this time a second or following train enters section 1ST, thesupply of feed back energy over the rails of this section will be cutoff and the relays L8AP and l-SAPP will become released to therebydiscontinue the supply of energy of 180 code frequency to the relayISCTM, and to supply energy of 75 code frequency thereto so that energyof "75 code frequency will be supplied to the rails of section [9T tocondition the locomotive -cab signal apparatus to display its yellow orcaution indication.

On release of relay lsAP contact 68 establishes the circuit includingfront contact 16 of relay Hill for supplying energy to the signalmechanism 18G, and as the contacts of the relay LBJ are released, thepolarity of the energy supplied to the mechanism MiG is such that thesignal will be conditioned to display its yellow or caution indicationif the signal lam-p were lighted. Accordingly, any light reflectedthrough the optical system of the signal will be consistent with theaspect displayed by the locomotive cab signal apparatus.

From the foregoing it will be seen that the modification shown in Fig. 3is arranged so that if the signal lamp is defective, the supply ofenergy of 180 code frequency to the adjacent section in the rear will becut off as soon as a train enters the section in the rear of the signaland energy of '25 code frequency will be supplied instead so that thecab signal equipment on the 10- comotive of the train will display itscaution indication and the train will approach the defective signal atreduced speed.

In addition, it will be seen that the system is arranged so that when asignal is defective and a train passes through the track stretch, thesupply of energy to the rails of the section in the rear of the sectionwith the defective signal is cut off so that the signal for the sectionin the rear of the defective signal will continue to display its stopindication after the section is vacated and as long as the section withthe defective signal is occupied. This insures that as long as thesection with the defective signal is occupied that the signal for thesection next in the rear will display its stop indication.

As there is in the rear of an occupied section one properly functioningsignal which is condie tioned to display its stop indication, followingtrains will be given ample warning of the presence of the first trainand will be prepared to stop before reaching the first train.

In addition, it will be seen that the'system is arranged so thatthe'mechanism of a signal with a defectivelamp is .conditioned to causelight refiected through the optical system of the signal to give anindication which is consistent with that given by the cab signalequipment on the 1. In a coded railway signaling system, in combination, a stretch of railway track having a pair of track railsdivided by insulated joints into a plurality of successive tracksections including a forward and a rearward section, means for supplyingcoded energy to the rails of said forward section, a track relayreceiving energy over the rails of said forward section, a signalgoverning trafiic in said forward section, said signal including a lamp,means responsive to code following operation of said forward sectiontrack relay and controlling the circuit of said signal lamp and alsocontrolling the supply of coded energy to the rails of said rearwardsection, means responsive to flow of energy in the circuit of said lampfor also controlling the supply of coded energy to the rails of saidrearward section, and traffic governing means responsive to the flow ofcoded energy in the rails of said rearward section.

2. In a coded railway signaling system, in com-, bination, a stretch ofrailway track having a pair of track rails divided by insulated jointsinto a plurality of successive track sections including a forward and arearward section, a signal governing traffic in said section, saidsignal including a lamp, means for supplying coded energy to the railsof said forward section, a track relay receiving energy over the railsof said forward section, an auxiliary relay associated with said trackrelay, means operative when and only when 'said' track relay isresponding to coded energy to energize the auxiliary relay, saidauxiliary relay being operative when released to establish a circuit tosupply energy tosaid signal lamp, means responsive to flow of current inthe circuit of said Gil bination, a stretch of railroad track having apair of track rails divided by insulated joints into a plurality ofsuccessive track sections including adjoining forward and rearwardsections, a signal governing movement of traffic in said forwardsection, said signal including a lamp, a track circuit for the forwardsection comprising means for supplying energy to the track rails at theexit end of the section and a track relay receiving energy from thesection rails at the entrance end of the section, means controlled bysaid track relay and operative when said relay is deenergized toestablish a circuit to supply energy to said. signal lamp, meansresponsive to the flow of energy in the circuit of said lamp andcontrolling the supply of coded energy to the rails of said rearwardsection, and indication means responsive to the flow of coded energy inthe rails of said rearward section.

4. In a coded railway signaling system, in combination, a stretch ofrailway track having a pair of track rails divided by insulated joint-sinto a plurality of successive track sections including a forward and arearward section, a signal'governing trafiic in said section, saidsignal including a lamp, means for supplying coded energy to the railsofsaid forward section, a track relay receiving energy over the rails ofsaid forward section, an auxiliary relay associated with said trackrelay, means operative when and only when said track relay is respondingto coded energy to energize the auxiliary relay, said auxiliary relaybeing operative when released to establish a circuit to supply energy tosaid signal lamp, a lightout relay included in series with said signallamp, means operative when the auxiliary relay is released provided thelightout, relay is picked up to supply coded energy to the rails of saidrearward section, and traffic governing means responsive to the flow ofcoded energy in the rails of said rearward section.

5. In a coded railway signaling system, in combination, a stretch ofrailway track having a pair of track rails divided by insulated jointsinto a plurality of successive track sections including a forward and arearward section, a signal for indicating occupancy of said forwardsection, said signal including a lamp, a track circuit for the forwardsection comprising means for supplying energy to the section rails atthe exit end of the section and a track relay receiving energy from thesection rails adjacent the entrance end thereof, means operative whensaid track relay is deenergized to establish the circuit of said signallamp, a lightout relay connected in series with said signal lamp, meansgoverned by said lightout relay and operative only when said relay ispicked up to supply coded energy to the rails of said rearward section,and trailic governing means responsive only to the flow of coded energyin the rails of said rearward section to provide a proceed indication,whereby said means will operate to provide a proceed indication when theforward section is occupied only if said signal lamp is lighted.

6. In a coded railway signaling system, in combination, a stretch ofrailway track having a pair of track rails divided by insulated jointsinto a plurality of successive track sections including a forward and arearward section, a signal for indicating occupancy of saidforwardsection, said signal including a lamp, a track circuit for the forwardsection comprising means for-supplying relay receiving energy from thesection rails adjacent the exit end of the section, an auxiliary relayassociated with said code following track relay, means operativewhen andonly when said track relay is responding to coded energy to en- 7. In acoded railway signaling system, in com-" bination, a stretch of railwaytrack having a pair of track rails divided by insulated joints into aplurality of successive track sections including a forward and arearward section, a signal for said forward section having a pluralityof lamps for indicating different degrees of trafiic restriction andincluding a first lamp providing a clear indication, a second lampproviding a caution indication and a third lamp providing a stopindication, indication means selectively responsive to the flow ofdifferent types of coded energy in the rails of the rearward section,means governed by traflic conditions in said forward section and in theadjoining section in advance for establishing circuits to light thefirst or the second lamp of said signal and to supply to the rails ofthe rearward section energy of a character effective to condition saidindication means to display its least restrictive aspect, meansresponsive to flow of current in the circuit of the first lamp andoperative on failure of flow of current therein to establish a circuitto light the second lamp, means responsive to the flow of current in thecircuit of the second lamp and operative on failure of flow of currenttherein to establish a circuit to light the third lamp and to change thecoded energy supplied to the rails of the section in the rear to acharacter effective to condition said indication means to display arestrictive aspect, means governed by traffic conditions in said forwardsection for establishing a circuit to also light said third lamp of saidsignal and to also supply to the rails of the rearward section codedenergy of a character effective to condition said indication means todisplay said restrictive indication, and means responsive to the flow ofcurrent in the circuit of the third lamp and operative on failure offlow of current therein to change the energy supplied to the rails ofthe section in the rear to a character effective to condition saidindication means to display its most restrictive indication.

8. In a coded railway signaling system, in combination, a stretch ofrailway track having a pair of track rails divided by insulated jointsinto a plurality of successive track sections including a forward and arearward section, a signal for said forward section having a pluralityof lamps and including a first lamp providing a clear indication, 2.second lamp providing a caution indication and a third lamp providing astop indication, indication means responsive to flow of coded energy ofa first character in the rails of the rearward section to provide aclear indication and to flow of coded energy of a second character -to'provide a caution indication, means governed by trafiic conditions insaid forward section and in the adjoining section in advance forestablishing circuits to light the first or the second lamp of saidsignal and to establish a circuit to supply coded energy of said firstcharacter to the rails of said rearward section, means responsive toflow of current in the circuit of the first lamp and operative onfailure of flow of current in said circuit to establish a circuit tolight the second lamp, means responsive to the flow of energy in thecircuit of the second lamp and operative on failure of flow of currentin said circuit to establish a circuit to light the third lamp and tochange the energy supplied to the section in the rear from coded energyof the first character to coded energy of the second character, meansresponsive to traffic conditions in said forward section forestablishing a-circuit to light the third lamp and to establish acircuit to supply coded energy of said second character to the-rails ofsaid rearward section, and means responsive to flow of current in thecircuit of said third lamp and operative on failure of flow of currentin said circuit to interrupt the supply of coded energy of said secondcharacter to the rails of said rearward section.

9. In a coded railway signaling system, in combination, a stretch ofrailway track having a pair of track rails divided into a plurality ofsuccessive track sections including a forward and a rearward section, asignal for said section having a plurality of lamps and including afirst lamp providing a clear indication, a second lamp providing acaution indication, and a thirdxlamp providing a stop indication,indication means responsive to flow of coded current in the rails ofsaid rearward section, said. means being operative on fiow of codedenergy of a first character to provide a ,clear indication and beingoperative on flow of coded energy .of asecond character to provide acaution indication, means operable when said forward section and theadjacentsection in advance thereof are both vacant to establish acircuit for the first lamp. including in series therewith a firstlightout relay andtoalso establish a circuit for supplying .coded energyof said first character to the railsof said'rearward section, meansoperable when said forward section and the adjacent sectionin advanceare both vacant and the first lightout relay is released to establish acircuit for the second lamp of said signal, means operable when said:forward section is vacant and the adjacent sectionin advance thereof isoccupied to establish a circuit for said second lamp of saidsignalincluding in series therewith a second lightout relay and to alsoestablish a circuit including a front contact of said second lightoutrelay for supplying coded energy of said first character to the rails.of said rearward section, means operable when said forward section isvacant and the adjacent section in advance is occupied and the secondlightout relay is released to establish a circuit for-the third lamp ofsaid signal and to alsoqestablish a circuit to supply coded energy ofsaid second character to the rails of said rearward section, meansoperable when said forward section is cocupied to establish a circuitfor the third lamp of said signal including in series'therewith a thirdlightout relay and to also establish a circuit including a frontcontact. of said third lightout relay for supplying coded energy of saidsecond character to the rails of said rearward section.

10. In a coded railway signaling system, in combination, a stretch ofrailway track havinga pair of track rails dividedby insulated jointsinto a plurality of successive track sections including a first, asecond and a thirdsection, a signal for and being operable on flow ofcoded energy of a .second character to provide a caution indication,

effective to produce a proceed indication will not,

"the second section having a lamp .and having mechanism for conditioningthe signal when lighted to display a clear, a caution or astop'indication, means for establishing a circuit for said lampincluding in series therewith a lightout re lay, indication meansresponsive to fiow of coded current in the rails of said third section,said means being operable on fiow of coded energy of a first characterto provide a clear indication means operable when said first and secondsections are vacant to cause said mechanism. to

condition saidsignal to display its clear indicate tion and to establisha circuit to supply coded215 energy of said first character to the railsof said third section, means operable when said first section isoccupied and said second section is vacant to cause said mechanism tocondition the signal to display its caution indication and toestablishpg a circuit including a front contact of said lightout relayfor supplying coded energy of said first character to the rails of saidthird section, means operable when said first section is occupied andthesecond section is vacant. and said lightout re- Z25 lay is releasedto establish a circuit for supplying coded energy of said secondcharacter to the rails of said third section, and means operablew-hensaid second section is occupied to cause said mechanism tocondition the signal to display its g stop indication and to establish acircuit including a-front contact of vsaid lightout relay for supplyingcoded energy of said second character to the rails of said thirdsection, whereby energy be supplied to the rails of the third sectionwhen a the second section is occupied and said signal lamp is defective.

11. In a coded railway signaling system, in combination, a stretch .ofrailway track havingggm a pair of track rails divided by insulatedjoints into a plurality of successive sections including a first, asecond and a third section, a signal for the second section having alamp and having mechanism for conditioning the signal when lighted todisplay a clear, a caution or a stop indication, an approach relayhaving a contact closed when said third section is occupied and operablewhen said contact is closed to establish a circuit for said lampincluding in series there- 50 with a lightout relay, indication meansresponsive to flow of coded current in the rails of said third section,said means being operable on flow of coded energy of a first characterto provide a clear indication and being operable on flow of coded energyof a second characterto provide a caution indication, means operablewhen said first and second sections are vacant. and the third section isoccupied to cause said mechanism to condition said signal to display itsclear indication and to establish, a circuit to supply coded energy ofsaid first character to the rails of said third section, means operablewhen said first section is. occupied and the second section is vacantand the third section is occupied to cause said mechanism to conditionsaid signal to display its caution indication and to establish a circuitto supply coded energy of said first character .to the rails of saidthird section if the lightout relay is picked up and to supply coded 70energy of said second character to the rails of said third. section ifsaid lightout relay is released, and means operable when the second andthird sections are occupied to cause said mechanism to condition saidsignal to display its stop indication and to establish a circuit tosupply coded energy of said second'character to the rails of said thirdsection if said lightout'relay is picked up and to cut off the supply ofcoded energy to the rails of said third section if said lightout relayis released.

12. In a coded railway signaling system, in combination, a stretch ofrailway track having a pair of track rails divided by insulated jointsinto a plurality of successive track sections, a signal for each sectioncapable of displaying a plurality of different indications including astop, a caution and a clear indication, each signal I including a lamp,each lamp having a lightout relay associated therewith, an energizingcircuit for each lightout relay including in series therewith theassociated signal lamp, a track relay for each section receiving energyover the rails of such section, each track relay having associatedtherewith a first decoding means including a first auxiliary relay whichis picked up when the track relay is responding to coded energy and asecond decoding means including a second auxiliary relay which is pickedup when and only when the track relay is responding to energy of thesecond code frequency, each such first auxiliary relay being operativewhen released to condition the associated signal to display its stopindication and when picked up to condition the signal to display aproceed indication, each such second auxiliary relay being operativewhen released provided the associated first auxiliary relay is picked upto condition the associated signal to display its caution indication andbeing operative when picked up provided the associated first auxiliaryrelay is also picked up to condition the associated signal to displayits clear indication, and means governed by each first auxiliary relayand the associated lightout relay for supplying energy to the rails ofthe adjacent track section in the rear, each such means being operativewhen said first auxiliary relay is picked up provided the lightout relayis also picked up to supply coded energy of the second code frequency tothe rails of said section and being operative when said first auxiliaryrelay is picked up and the associated lightout relay is released tosupply coded energy of the first code frequency to the rails of saidsection, said means being also operative when the first auxiliary relayis released to supply coded energy of the first code frequency to therails of said section.

13. In a coded railway signaling system, in combination, a stretchrailway track having a pair of track rails divided by insulated jointsinto a plurality of successive track sections including a forward and arearward section, a signal for the forward section including a lampwhich becomes lighted to cause the signal to display an indication, atrack relay for the forward section receiving energy over the rails ofsaid section, means for at times supplying energy of a first codefrequency and at other timessupplying energy of a second code frequencyto the rails of said forward section, a first decoding means associatedwith said track relay and including a first auxiliary relay which ispicked up when the track relay is responding to coded energy and asecond decoding means including a second auxiliary relay which is pickedup when the circuit of said decoding means is'established and the trackrelay is responding to energy of the second code frequency, said firstauxiliary relay being operative when released to condition-the signalwhen lighted to display a stop indication and 'to effect. the supply ofenergy of the first code frequency to the rails of said rearward sectionand being. operative when picked up to condition said signal to displaya proceed indication and to effect the supply of energy of the secondcode frequency to the rails of the'rearward section, said secondauxiliary relay being operative when released provided the firstauxiliary relay is picked up to condition the signal to display itscaution indication and when picked up provided thefirst auxiliary relayis also picked up to con dition the signal to display its clearindication, indication means for said rearward section responsive toflow of coded-energy in the rails of said section, an approach relaywhich is released when the rearward section is occupied, a slowreleasing repeater relay energized when said ap proachrelay is picked:up, a lightout relay connectedin series with the lamp of the signal forsaid forward section, a circuit including a front contact of saidrepeater relay and a back contact of said approach relay'for energizingsaid second decoding means, a circuit including back contacts of saidapproach relay and said repeater relay for energizing said signal lampand said lightout relay, and a circuit including a front contact. ofsaid lightout relay for also energizing said second decoding means.

14. In a coded railway signaling system, in 0 combination, a stretch ofrailway track having a pair of track rails divided 'by' insulated jointsinto a plurality of successive track sections including a forward and arearward section, means for supplying coded energy -to the rails ofsaidi forward section, a code following track relay having a windingreceiving energy over' the rails of said forward section, an auxiliaryrelay associated' with said track relay, means responsive to codefollowing operation of said track relay for supplying energy to saidauxiliary relay, a signal governing traflic in said forward section,said signal including a lamp, a lightout relay, a circuit including saidlamp in series therewith for energizing said lightout relay, meansgoverned by -said auxiliary relay and said lightout relay for supplyingcoded energy to the rails of said rearward section, said means beingoperative when said auxiliary relay is picked up provided the lightoutrelay is also picked up to supply coded energy of a' first character tothe rails of said rearward section and being operative when saidauxiliary relay is picked up and the lightout relay is released tosupply coded energy of a second character to the rails of said rearwardsec-' tion, said means being also operative to supply coded energy ofsaid second character to the rails of said rearward section when saidauxiliary relay is released, and traflic governing means selectivelyresponsive to the flow of coded energy of said first and secondcharacters in the rails of said rearward section, said means beingoperative in response to flow of coded energy of the first character toprovide a first proceed indication and being operative in response toflow of coded having a, winding receiving energy over the rails of saidforward section, an auxiliary relay associated with said track relay,means responsive to code following operation of said track relay forsupplying energy to said auxiliary relay, a signal governing traflic insaid forward section, said signal including a lamp, a lightout relay, acircuit including said lamp in series therewith for energizing saidlightout relay, means governed by said auxiliary relay and said lightoutrelay for supplying coded energy to the rails of said rearward section,said means being operative when said auxiliary relay is picked upprovided the lightout relay is also picked up to supply coded energy ofa first character to the rails of said rearward section and beingoperative when said auxiliary relay is picked up and the lightout relayis released to supply coded energy of a second character to the rails ofsaid rearward section, said means being also operative to supply codedenergy of said second character to the rails of said rearward sectionwhen said auxiliary relay is released and said lightout relay is pickedup and being operative to prevent the supplyof coded energy of eithercharacter to the rails of said rearward section when said auxiliaryrelay and lightout relay are .both released, and traflic governing meansselectively responsive to the flow of coded energy in the rails of saidrearward section, said means being operative in response to flow ofcoded energy of the first character to provide a first proceedindication and being operative in response to flow of coded energy ofthe second character to provide a restrictive proceed indication andbeing operative in response to the absence of flow of coded energy toprovide the most restrictive indication.

16 In a coded railway signaling system, in combination, a stretch ofrailway track having a pair of track rails divided by insulated jointsinto a plurality of successive track sections includinga forward and arearward section, means for supplying coded energy to the rails of saidforward section, a code following track relay having a winding receivingenergy over the rails of said forward section, an auxiliary relayassociated with said track relay, means responsive to code followingoperation of said track relay for supplying energy to said auxiliaryrelay, a signal governing traflic in said forward section, said signalincluding a lamp, a lightout relay, an approach relay governed bytraffic conditions in said rearward section, said approach relay beingenergized when said rearward section is vacant and being effective whendeenergized to establish a circuit including said lamp and said lightoutrelay in series, a circuit including front contacts of the approachrelay and of the auxiliary relay for supplying coded energy to the railsof the rearward section when the approach relay is energized providedthe auxiliary relay is also energized, and a circuit including frontcontacts of the auxiliary relay and of the lightout relay for alsosupplying coded energy to the rails of the rearward section when theapproach relay is released provided the auxiliary relay'and the lightoutrelay are both energized.

RALPH R. KEMMERER.

